SF 







UNITED STATES DEPARTMENT OF AGRICULTURE 




jyJ^'^Lru 



BULLETIN No. 996 

Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER, Chief 




Washington, D. C. 



October 12, 1921 



FLUSHING AND OTHER MEANS OF INCREASING LAMB 

YIELDS. 1 

By FT Rf Marshall and C. G. Potts, Animal Husbandry Division. 



CONTENTS. 



Page. 
Extent to -which flushing is practiced in the 

United States 1 

Factors influencing size of lamb crop 2 

Results of experiments in flushing ewes :i 

General plan of the experiments 3 

Number of lambs dropped ! 

Relation of weight gains to number of twins. 6 

Feed for flushing t; 

Earlinass of lambing 6 

Uniformity of lambs' ages 7 



Twin production as affected by age of ewe. . . V 

Twin production as affected by breed of ewe. 8 

Twin production as affected by sire 8 

Breeding for twin lambs 9 

Value of twin lambs in comparison with 

singles i o 

Comparative weights of single and twin lambs 11 

Summary 13 



EXTENT TO WHICH FLUSHING IS PRACTICED IN THE UNITED STATES. 

THE BELIEF that extra feeding of ewes at the time they were 
bred would result in larger yields of lambs has long been held 
by students of sheep husbandry. Feeding for this purpose is 
commonly called "flushing." Though flushing has been practiced 
by a few breeders of purebred slice]), it has not been generally or 
seriously considered by Hock owners producing market lambs. 
Practically no figures or results of experiments have been obtainable 
as to the extent of increase in the lamb crop that could be obtained 
by flushing the ewes. 

This bulletin presents the results of live years' experiments in Hush- 
ing ewes, covering a total of 302 matings. These experiments were 
conducted on that portion of the Bureau of Animal Industry farm at 
Beltsvillc, Md., known as "Sheep Acres," and at the United States 
Morgan Horse Farm, Middleburv. Vt. There is added a discussion 
of other matters to be considered in endeavoring to obtain maximum 
yields of lambs. 



!R. B. Millin, now of the Montana Agricultural College, assisted in the early development of the experi- 
ments reported in this bulletin. 

56405°— 21— Bull. 996 









2 BULLETIN 996, U. S. DEPARTMENT OF AGRICULTURE. 

FACTORS INFLUENCING SIZE OF LAMB CROP. 

The size of the lamb crop is dependent upon two things — the num- 
ber of dry ewes (those not having lambs) and the number of twins 
and triplets. Under ordinary farm-flock conditions the proportion of 
dry ewes is insignificant. In range flocks, however, it is a principal 
cause of lower lamb yields, and it is often impossible to furnish the' 
feed necessary to put the ewes into condition to make sure of their 
getting in lamb. 

The advantages of flushing are to be obtained principally through 
an increased number of twins. It has not been proved that the sire 
influences the number of twins occurring among his offspring. The 
production of twins or triplets is determined chiefly, if not entirely, 
by the ewe. Twins may result in either of two ways. First, two 
developed ova (eggs) may be discharged from the ovaries during the 
period of heat. Second, a single fertilized ovum may become divided 
at an early stage and each part develop a fetus. The first is believed 
to be the more common cause of twins. The production of a second 
or third ovum is thought to be largely influenced by the condition 
of the ewe and on this basis the connection between flushing and twin 
births is rendered very clear. 

To show the connection between production of twin lambs and 
maturing of extra ova, Marshall 2 slaughtered 55 Black-faced High- 
land sheep shortly after breeding and examined the ovaries to learn 
the number of ova that were produced. His findings were as follows: 

1 ruptured follicle in one ovary — 1 ovum produced 42 cases. 

1 ruptured follicle in each ovary — 2 ova produced 7 cases. 

2 ruptured follicles in one ovary — 2 ova produced 5 cases. 

2 ruptured follicles in one ovary and one in the other — 3 ova produced .... 1 case. 

In this case if the ewes had been kept and if all the ova had been 
fertilized and all developed normally, the result would have been 42 
single lambs, 12 pairs of twins, and one set of triplets, a total lamb 
crop equal to 125.4 per cent of the number of ewes bred. The report 
of this experiment states that this is higher than the ordinary returns 
from flocks of the breed and that apparently under ordinary condi- 
tions some of the ova do not produce lambs. 

It is a common observation that the twin lambs in a flock are pro- 
duced chiefly in the early part of the lambing season. In 302 cases 
of lambing in purebred Southdown ewes used in experiments con- 
ducted by the Bureau of Animal Industry and extending over five 
years, 78 per cent of the ewes dropping twins lambed during the first 
half of the lambing period. 

The explanation of these facts must be found in one of two things, 
either of which has an important relation to management for maxi- 

2 The (Eslrous Cycle and the Formation of Corpus Luteum in Sheep. In Philosophical Transactions of 
the Royal Society, Series B, No. 196, 

LIBRARY OF cONQKflt 
•'•.FKcovto 

ooouMENTs ammo* 



w 



FLUSHING TO INCREASE LAMB YIELDS. 



mum lamb yields: (1) The ewes that are in the best nourished condi- 
tion and therefore more likely to produce two ova are also those 
first to come in heat and get in lamb, or, (2) the feed and pasturage 
are more nutritious early in the season and cause production of more 
ova by the ewes bred at that time. 

In the Bureau of Animal Industry experiments the use of rams 
began about September 7 to September 10, but in most cases only 
one or two ewes were bred during the first 10 days. It therefore 
seems that the ewes ordinarily bred first are those that owing to 
their better physical condition first come in heat at the beginning 
of the breeding season, and that their condition is at once the cause 
of their showing heat earlier and their producing twins. 

An overfat condition may derange the normal action of the ova- 
ries even more seriously than a thin condition. It seldom occurs 
except in stock fitted for show or in ewes that have missed getting in 
lamb and grown fat while running dry. In our experiments there 
have been some rather fat dry ewes which got in lamb as readily as 
other ewes. They were not allowed grain, however, and had plenty 
of exercise. 

RESULTS OF EXPERIMENTS IN FLUSHING EWES. 

GENERAL PLAN OF THE EXPERIMENTS. 

The experiments were made with purebred Southdown ewes, all 
of which had been bred in the Bureau of Animal Industry flocks. 
The number of animals was 302, divided into 17 lots, of which Lots 
1, 2, 5, and 6 were at the Morgan Horse Farm, Middlebury, Vt., 
and Lots 3, 4, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and 17 at the bureau 
farm, Beltsville, Md. The ewes were usually in good condition com- 
pared with general farm flocks, which it is thought would tend to 
lessen the effect of flushing. 

In all the tests the lots of ewes were divided with careful regard to 
age, number of lambs dropped in previous years, gain in weight prior 
to experiment, and the rams to which bred. As it was necessary to 
use a number of different rams in each flock, hand breeding 3 was 
followed, which with the use of teasers 4 made it possible to record 
the date of each service and at the same time mate each ewe to the 
ram desired. Approximately the same number of ewes in each lot 
were bred to each of the rams used that season. In one case the 
proportion was disturbed because one of the rams was not a sure 
breeder and some of the ewes booked to him did not get in lamb. 
Such cases were eliminated from the experiment. The data given 
are in all cases for ewes having lambs. The matter of dry ewes and 
the influence of rams upon the lamb yield are discussed separately. 

3 " Hand breeding " is a term applied to the individual mating of a ram and ewe outside the flock. 
« ' ' Teaser " applies to a ram used in a flock for t he purpose of indicating the ewes which are in heat. Copu- 
lation is prevented by an apron tied around the ram's body. 



4 BULLETIN 996, U. S. DEPARTMENT OF AGRICULTURE. 

The amount of grain fed was never less than one-half pound per 
ewe daily; in a few cases it was as much as three-fourths of a pound. 
The grain mixture used is given in Table 1. The gains shown are 
the averages for each lot, each ewe's gain covering the period 
from one to two weeks prior to the dates the rams were first used up 
to the date of the service to which she lambed. 

It was planned to hold the unflushed lots without making any gains 
in weight during the breeding season. Except in the case of Lots 1 1 
and 14, the pasturage was the same for the flushed and unflushed lots. 
There was considerable irregularity in the gains of individual ewes. 
Some of those in the unflushed lots made quite large gains, while 
some in the flushed lots made little or no gain. However, the fact 
of having grain feed may be considered to result in a more highly 
nourished body condition, even if not reflected in gains in weight . 

In all the Vermont flock tests, all lots were run on blue-grass pas- 
tures. All the lots in the Maryland flock were grazed on forage 
crops, soy beans being chiefly used during the breeding season. 

NUMBER OF LAMBS DROPPED. 

An average increase of 18.1 per cent in the number of lambs dropped 
was obtained as a result of flushing in the experiments here reported. 
This figure applies to 302 lambings of 143 different ewes used in the 
fall breeding seasons of 1916 to 1920, inclusive, and includes the total 
number of lambs dropped, living or dead, the percentage being based 
on the number of ewes having lambs. 

As shown in Table 1, the smallest result from flushing obtained in 
any one of the separate trials was 3.2 per cent. This was in the case 
of Lots 5 and 6, bred at the Morgan Horse Farm, Middlebury, Vt., in 
the fall of 1917. Both lots of ewes were in very good condition and 
ran on similar grass pastures. Although fed grain (14 parts corn, 5 
parts bran, 1 part linseed-oil meal) at the rate of one-half pound each 
daily, the flushed lot made an average gain of only 6.3 pounds per 
head from September 10 until they were in lamb, while in the corre- 
sponding time the ewes not fed grain gained 4.6 pounds per head. 

The most pronounced effects of flushing are seen by comparing 
Lot 3 with Lot 4 and Lot 9 with Lots 10 and 11. In the case of Lots 
3 and 4, both of which were in quite low condition when breeding 
commenced, there was an increased gain of 12.38 pounds in weight in 
the flushed over the unflushed lot and an increase of 30 per cent in 
lambs dropped. In the second instance the 15 unflushed ewes (Lot 
9) gained 3.03 pounds each from September 10 to the time of getting 
in lamb, the average date of which was October 5. This lot produced 
120 per cent of lambs. During the same time 150 per cent of lambs 
was yielded from a lot of 14 ewes (Lot 10) receiving grain, and 145.5 
per cent for 11 ewes (Lot 11) kept on sufficiently good pasture to 
cause them to gain 10.96 pounds each from September 10 until in 
lamb., the average date being October 14. 



FLUSHING TO INCREASE LAMB YIELDS. 



Lambs 
dropped. 


I't CI II 1 . 
140 
140 

140 
161. 5 
L50 
145.5 
147.6 

152. 1 

150 

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6 BULLETIN 906, U. S. DEPARTMENT OF AGRICULTURE. 

Breeds having a larger proportion of twin births than the South- 
downs can be expected to give larger returns from flushing. Also, 
most farm ewes should show larger increases in lamb yields as a 
result of flushing than were obtained in these experiments because 
of the fact that ordinarily they are thinner at the time of breeding. 

RELATION OF WEIGHT GAINS TO NUMBER OF TWINS. 

Individual weights of the ewes were kept, and these permit an 
analysis of the relation between actual gains and numbers of twins 
prpduced. 

Of 30 cases in which ewes lost 1 to 7 pounds during the breeding 
season, twins were produced by 11, or 37 per cent. 

Of 133 cases in which ewes gained up to 7 pounds during the breed- 
ing season, twins were produced by 45, or 34 per cent. 

Of 74 cases in which ewes gained 7 to 30 pounds during the breed- 
ing season, twins were produced by 33, or 44 per cent. 

These results suggest that in order to produce the largest number 
of twins, ewes should gain 7 pounds or more. 

FEED FOR FLUSHING. 

With regard to kinds of feed most effective and most economical 
for use in flushing, no data have been obtained except in the cases 
of Lots 11 and 14. These lots had first access to good growths of 
soy beans, while the grain-fed lots and the unflushed lots followed on 
the same grazing after the pasture-flushed lots were moved forward. 
The difference in the grazing so obtained caused Lot 11 to gain 3 
pounds more than Lot 9 in 1918 and Lot 14 to gain 4 pounds more 
than Lot 12 in 1919. In 1918 the pasture-flushed Lot No. 11 pro- 
duced 4.5 per cent fewer lambs than the grain-flushed Lot No. 10, 
while in 1919 the pasture-flushed Lot No. 14 produced 4.8 per cent 
more lambs than the grain-flushed Lot No. 13. 

This would indicate that there is no decided advantage in the 
kind of feed used in flushing other than the saving in labor and 
more expensive grain feed when pasture flushing is practiced. There 
are times, however, owing to unfavorable weather, when good pas- 
ture is not available and pastures are too short even to hold ewes 
at their initial weight. In such cases grain could no doubt be 
economically used. 

EARLINESS OF LAMBING. 

In addition to the increase in the number of lambs from flushed 
ewes, it has been believed that the extra nourishment brought the 
ewes in heat earlier and thereby resulted in earlier lambs. This is a 
reasonable expectation when the rams are in service at the beginning 
of the breeding; season. 



FLUSHING TO INCREASE LAMB YIELDS. 



In all but two cases flushed ewes came to the first service earlier 
than those unflushed, the time ranging from one-half day to 8 days. 

UNIFORMITY OF LAMBS' AGES. 

Having all the lambs of about the same age is a great advantage 
in marketing and flock management. Since flushing brings ewes to 
service earlier, it should be a great aid in preventing late lambs. 
This expectation was not realized, however, in the experiments. 
More of the cases of not getting in lamb until the second or third 
service occurred among the flushed ewes and was of course followed 
by a larger proportion of late lambs. 

The number of ewes lambing to each successive service in each 
year is shown in the following table; the ewes which were bred after 
being interchanged between lots are not included : 

Table 2. — Number and per cent of ewes getting in lamb at each servici . 





Unflushed lots. 


Flushed lots. 


Year. 


Lot 
No. 


Ewes 
in 
lot. 


Service. 


Lot 
No. 


Ewes 
in 
lot. 


Service. 




1st. 1 2d. 


3d. 


4th. 


5th. 


1st. 

10 
7 

i:, 
6 

11 
7 
6 

12 

13 
9 


2d. 


3d. 


Hh. 


5th. 


1916 


1 
3 
5 

7 
9 


15 
10 
19 
17 
15 


8 

15 

7 
1 t 


5 
4 
3 
4 
1 


2 
5 
1 

.5 




1 

1 

•0 









2 
4 
6 
8 
10 
11 
13 
14 
16 
17 


25 

15 
20 
13 
14 
11 
21 
21 
20 
16 


id 
7 
3 
3 
3 
2 
7 
3 
4 


3 
1 
2 
3 

1 
6 
6 
2 


1 


1 



1 

2 

(1 

1 
1 


1 










1917 


1918 






1919 


12 


- 25 


13 9 


2 


1 







1920 


15 


20 


U 8 





1 

























Total . . . 




121 


6S 34 
56 28 


15 
13 


4 
3 








176 


96 40 25 

5:. -v, ii 


7 

4 


2 


Percent. 

























TWIN PRODUCTION AS AFFECTED BY AGE OF EWE. 

Flock records of the Bureau of Animal Industry show a gradual 
rise in the proportion of twins born until the ewes are 5 and 6 
years old. There is a possibility that this is due in part to elimination 
of ewes not dropping twins. In our experimental flocks, however, 
ewes have never been discarded on that account, although some ev\ ts 
have been kept to advanced age that might have been disposed of 
one or two seasons earlier if it had not been for their marked prolifi- 
cacy. The figures given in Table 3 for ewes over 6 years old may, 
therefore, have been to a slight extent affected by selection. The 
data given include nine years' records. The ages are those at time 
of lambing and not at time bred. 



8 BULLETIN 996, U. S. DEPARTMENT OF AGRICULTURE. 

Table 3.- -Effect of age of ewes on per cent of lambs dropped in experimental flocks. 



Age of ewes. 


('uses Of 

lambing. 


Lambs 

dropped. 


Age of ewes. 


Cases of 
lambing. 


Lambs 

dropped. 


Years. 
2 


79 
63 
67 
62 


Per a nt. 

in. i 
123.8 
143. 3 
143.5 


Years. 
6 


49 

35 

22 

8 


Pir cent. 
161.2 


3 


7 


112. 8 


4 


8 


113.6 


;, 


9 


162. 5 









TWIN PRODUCTION AS AFFECTED BY BREED OF EWE. 

Evidence as to inheritance of fertility makes it appear that vari- 
ous breeds or strains have each an inherited limit of fertility and that 
the obtaining of the full possibility in any one season will be deter- 
mined by the extent to which the conditions and management favor 
the full utilization of the inherited capacity. 

Records of actual returns from 189 flocks representing 9 breeds for 
the seasons of 1919 and 1920 were obtained by the Animal Husbandry 
Division through the kindness of breeders who reported. The aver- 
age per cent of lambs in proportion to ewes, lambing in the spring, is 
shown below, also the separate record of the 2-year-old ewes (drop- 
ping lambs the first time) and the highest flock average reported for 
each breed. The table gives the average of the two seasons' reports. 
The high return for the breed is for a single season. 

Table 4. — Record of lamb crops, bi/ breeds, from 189 flocks. 
[Average of seasons 1919 and 1920.] 





Flocks. 


2-year-old ewes. 


Aged ewes. 


Total ewes. 


Highest flock. 


Breed. 


Ewes. 


Lambs 
dropped. 


Ewes. 


Lambs 
dropped. 


Ewes. 


Lambs 
dropped. 


Ewes. 


Lambs 
dropped. 




Number. 
26 
11 
IS 
27 
26 
16 
25 
16 
24 


Number. 
215 

40 

96 
138 
549 

91 
167 

84 
186 


Per cent. 
146 
145 
144 
143 
139 
135 
134 
123 
111 


Number. 
566 
106 
214 
378 
857 
190 
402 
184 
667 


Per cent. 
163 
161 
156 
153 
148 
148 
154 
149 
125 


Number. 
7sl 
146 
310 
516 
1,406 
281 
566 
268 
853 


Per cent. 
158 
157 
152 
151 
144 
141 
119 
141 
122 


Number. 
6 

11 
6 
6 
6 

23 
6 
8 
9 


Per cent. 
200 




191 


Oxford.... 


200 


Southdown 


200 
200 




200 




183 




200 


Rambouillet 


177 



TWIN PRODUCTION AS AFFECTED BY SIRE. 

A study of 334 cases of lambing from the services of 5 rams, none 
of which were used less than three seasons or on less than 20 ewes, does 
not indicate any important variation in proportions of twins that can 
be attributed to the sire. Such differences as were shown in the 
average number of lambs per service for each sire appeared to be due 
to differences in the ewes to which they were bred. Records of 380 
lambings from services of 8 different sires were studied in relation to 



FLUSHING TO INCREASE LAMB YIELDS. 9 

the ages of the rams at the time of service. The results did not show 
any connection between age of sire and number of twins among 
his "get." 

Overworked or run-down condition of a ram may result in a smaller 
lamb crop through a lack of numbers or of vitality of the sperm cells 
in the seminal fluid. Such a lack is most likely to occur in the case 
of ram lambs running in a flock with the ewes, and it would be more 
likely to result in ewes not getting in lamb than in a decreased number 
of twins. Though improbable, it is possible that a ewe might pro- 
duce two" ova and have one of them fail to become fertilized because 
of a lack in the number or vitality of the sperm cells. 

BREEDING FOR TWIN LAMBS. 

It appears quite logical to suppose that the proportion of twin 
births in a flock can be increased by selecting, for breeders, rams and 
ewes themselves born as twins. However, the facts do not bear 
out such a supposition. This does not preclude the possibility of 
increasing lamb yields by breeding, but selection for this purpose 
should be based on average yields of different strains rather than on 
records of individuals. 

The fact that a ram was born as a single or as a twin can not reason- 
ably be expected to have any relation to the number of twins among 
his offspring. The function of the sperm cells of the male is to 
fertilize the ova produced by the female, and under ordinary condi- 
tions the number and strength of the sperm cells is many times greater 
than actually needed. 

It is reasonable, however, to expect a son of a ewe that is a regular 
producer of twins to transmit some or all of his dam's capacity to 
his daughters. Any ewe's inheritance of capacity for bearing twins 
must therefore be traced through the prolificacy records of her female 
ancestors. 

In the breeding of the bureau's purebred Southdown flock, records 
have been obtained of 458 cases of lambing which include only ewes 
that have dropped lambs at least three times. A few of the ewes 
had eight or nine lambing records. The relation of the production 
of these ewes, the fact of their having been born as single or twin 
lambs, and also whether their sires and dams were born as singles or 
twins are shown in Table 5. It must be remembered that the fact of a 
ram or a ewe having been born as a single or twin is in itself an 
incomplete record of the dam's productive rapacity. 

As shown in the table twin-born ewes were found to be 4.7 per cent 
more prolific than those born singles. The highest record, however, 
is from ewes born as singles with both parents twins, and the second- 
highest record is for single-born ewes by single sires from twin dams. 



10 



BULLETIN 996, U. S. DEPARTMENT OF AGRICULTURE. 



There does not appear to be any connection between lamb produc- 
tion and the fact of sires and dams having been singles or twins. 

Table 5. — Effect of breeding on twin production of Southdown ewes in Government flock. 



Ewes' breeding. 



Number 
of ewes. 



Number 

of 
lambings. 



Lambs 
dropped 



Born twins: 

Sires twins, dams twins. . . 
Sires singles, dams twins . . 
Sires twins, dams singles. . 
Sires singles, dams singles. 

Average for twin ewes . . . 

Born singles: 

Sires twins, dams twins . . 
Sires singles, dams twins. . 
Sires twins, dams singles . . 
Sires singles, dams singles . 

Average for single ewes . 



12 
84 
12 
L34 



Per cent. 
133 
142. g 
116.6 
142. 5 



140.9 



14 
70 
21 
111 



157.1 
145.7 
109.5 
132.7 



136.2 



A safer way of appraising the possibility of increasing twin pro- 
duction by selection is to take into account the full records of female 
ancestors rather than a single birth in which the particular sire or 
particular dam was produced. 

VALUE OF TWIN LAMBS IN COMPARISON WITH SINGLES. 

Sheep raisers differ in their ideas of the desirable size of the lamb 
crop. At one extreme are ranchmen chiefly interested in wool pro- 
duction who consider twins as undesirable because feed conditions 
are unfavorable to a ewe's furnishing more than sufficient milk for 
one lamb. Even in such cases, however, it is always likely that a 
number of ewes will lose their lambs and a corresponding number of 
pairs of twins would allow transferring one from each pair of twins 
to a ewe in milk and without a lamb. This would render possible 
the rearing of 100 per cent of lambs. 

There are, also, a few breeders of registered sheep who believe that 
there is no gain in obtaining twin lambs. Their position is based 
upon the fact that some twin lambs do not develop so fully as singles. 
Since a good individual animal sold for breeding purposes may bring 
as much as or more than two inferior ones, single lambs might be an 
advantage, provided they always proved more valuable at selling age. 

At the other extreme are raisers of market lambs in whose hands a 
pair of twins, even though comparatively underdeveloped and sold 
perhaps at a lower price per pound, still will bring a much larger 
amount than the single lamb. 

With ewes lambing for the first time, it is less desirable to have 
twin lambs than with older ewes. Young ewes do not ordinarily 
milk so well nor look after their lambs so faithfully, and thus they 



FLUSHING TO INCREASE LAMB YIELDS. 



11 



have a greater rate of loss in twin lambs than older ewes. In most 
flocks, if not all, containing the ordinary proportion of ewes of vary- 
ing ages, the mark can well be set at 150 per cent of lambs in working 
for the greatest net returns. 

Possible disadvantages in twin lambs must come from one or all of 
three causes: (1) Greater rate of loss among twins; (2) slower rate 
of growth as lambs; or (3) inability to reach the same size, weight, 
and breeding value as single lambs. 

As regards the rate of loss, the experience of the Bureau of Animal 
Industry shows no greater losses among twins. In the lambing 
seasons of 1916 to 1920, inclusive, in the two flocks of Southdowns 
used in the experiments a total of 224 single lambs and 290 twin 
lambs was born. Of these 14.3 per cent of the single-born lambs 
died before reaching the age of 2 weeks, and 13.4 per cent of the 
twins. 

COMPARATIVE WEIGHTS OF SINGLE AND TWIN LAMBS. 

Comparative weights of twins and single lambs at six months old 
show that the milk received by the lambs is more important in in- 
fluencing growth than is birth as a single or twin. 

Records of 184 lambs dropped through three different years are 
grouped to show weights attained by both sexes and by single lambs, 
twin lambs, and lambs born as twins but having all of one ewe's 
milk (twins raised as singles) . The weights of the ram lambs include 
3 or 4 wethers. 



Table 6. — Weights of 6- months-old twin and single lambs. 





Singles. 


Twin-. 


Twins raised as singles. 


Kind. 


Number. 


Average 

weight. 


Number. 


Average 
weight. 


Number. 


Average 
weight . 




32 
46 


Pounds. 
85.4 
73.8 


45 
37 


Pounds. 
81.6 

07.6 


9 
15 


Pounds. 

82 7 




78 3 








78 


78.6 


82 


75.3 


24 


79.9 







The twin-born ewe lambs averaged 6 pounds lighter at six months 
than those born singles, while in the case of ram lambs the difference 
was 4 pounds. In the smaller groups of twin lambs raised as sin- 
gles the ewes made an especially good growth, averaging more than 
the single lambs. 



12 BULLETIN 996, U. S. DEPARTMENT OF AGRICULTURE. 

Three experiments were conducted to determine whether twin ewe 
lambs would catch up in weight with the singles if given an oppor- 
tunity. Of the 1915 crop, 19 head of singles and 22 twin-ewe lambs 
were fed separately for 112 days (December 8, 1915, to March 28, 
1916). At the outset the singles were 8.6 pounds heavier and at the 
close of the test they were 1 1 pounds heavier. They received similar 
feed, but that eaten by the twins contained about 6 per cent more 
total energy. After running in the same lot on pasture until August 
30, 1916, the single-born lambs were still 8 pounds heavier. 

In November, 1916, 8 head of single ewe lambs and 8 head of twins 
that had been raised as twins were placed in a similar experiment. 
The average daily ration fed the twins contained 0.28 pound of pro- 
tein and 1.84 therms of energy as compared with 0.24 pound of 
protein and 1.57 therms of energy for the singles. At the start the 
singles were 7 pounds heavier and at the close of the special feeding 
the weights were identical. The twins were somewhat fatter, how- 
ever, and after running with the others on pasture until August 25, 
1917, were 2.4 pounds lighter. 

In the summer of 1917 an attempt was made to furnish lambs 
raised as twins sufficient extra grain to permit them to catch up with 
those born singles. From birth (about March 1) until July 1, there 
were 11 single ewe lambs and 3 born twins but raised as singles in 
one lot, and 8 twin-raised ewe lambs in the other lot. During that 
time the former ate 50 pounds of grain each and the twins 63 pounds, 
with the result that the twin lambs averaged 7 pounds lighter than 
the others. Subsequently the lambs were fed and pastured as one 
lot until December 29, 1917, at which time the singles were 3 pounds 
heavier. From December 29, 1917, to April 6, 1918, the single lambs 
ate an average daily ration of 1 pound of the following grain mix- 
ture: Cracked corn 100 parts, bran 30 parts, in connection with 2 
pounds timothy hay and 2 pounds turnips per head. That eaten by 
the twin lambs consisted of If pounds of a mixture consisting of 
cracked corn 80 parts, oats 60 parts, bran 35 parts, in connection 
with 2 pounds of timothy hay and 2 pounds of turnips. On April 6 
the singles weighed 107 pounds and the twins 1 10. That their extra 
gain was not fat is shown by the fact that after running on pasture 
with no feed until August 10, the twins were 3.1 pounds heavier per 
head than the singles. A comparison of the gains made by singles, 
twins raised as twins, and twins raised as singles is shown in Table 7. 

The fact that lambs born as twins but receiving all of one ewe's 
milk often equal and sometimes outweigh single lambs makes the 
matter appear to be one of nourishment. The slight lack of growth 
and development of twin-ewe lambs below that of singles at market 
age is not serious in comparison with the advantage of larger numbers. 



FLUSHING TO INCREASE LAMB YIELDS. 



13 



Table 7. — Gains made by single and twin lambs in bureau flocks at Middlebury, 17., 

and Beltsville, Md. 





Single lambs. 


Twin lambs raised as 


(wins. 


Twin lambs raised as singles. 






Averag 


e weight. 






Average weight. 




Average weight. 
































03 










<3 










C3 












£) 


,d 


o 


o 


o 

e 


& 


s, 




c 


z 


■d 


,g 


g 


o 


o 




6 


L 


ft 


a 


6 


£ 


= 


n 


a 


o 


a 


fl 


R 


a 




S3 


pa 


M 


<o 




S3 


« 


m 


«o 




* 


M 


CO 


to 




M i d d 1 ebury 
































flock: 
































1916— Rams. . . 


5 


9.0 


75.6 


97.1 


130.8 


9 


9.2 


68. 2 


89.4 


131.0 


1 


7.8 


68.0 


84.0 


109.0 


Ewes 


8 


9.2 


64.8 


77.9 


(') 


10 


7.5 


55.6 


67.9 


(') 


8 


7.8 


65. 5 


81. 1 


114.4 


1917— Rams. . . 


5 


7.9 


66.8 


94.8 


117.4 


4 


7.6 


59.5 


84. 3 


108. 5 


4 


7. s 


57.5 


87. 3 


118.0 


Ewes 


11 


8.3 


61.7 


78.8 


106.7 


8 


7.5 


55.9 


76.5 


109.6 


3 


7. 1 


67.0 


84.3 


111.7 


191S— Rams... 


8 


8.6 


56.4 


84.8 


121.8 


12 


7.4 


49.8 


77.9 


117. s 


1 


7.3 


51.0 


83.0 


119.0 


Ewes 


13 


8.8 


54.1 


76. S 


113.7 


11 


6.9 


38.2 


63.8 


107. 5 


2 


6.1 


41.0 


68. ."> 


101.0 


Average: 
Rams 


1.8 


8.5 


64.6 


91.1 


123.1 


25 


8.1 


5S.0 


83.1 


121.0 


6 


7.7 


58. 1 


86.0 


116.6 


Ewes 


32 


8.7 


59.4 


77.9 


110.5 


29 


7.3 


49.1 


68.9 


ION. 4 


13 


7.4 


62.1 


79.9 


111.7 


Beltsvilb flock: 
































1917— Rams . 


2 


8.4 


40.5 


69.0 


96.0 


3 


6.9 


45.2 


73. 5 


94.7 


2 


6.2 


38.8 


67. 8 


91.8 


Ewes.. 


8 


7.7 


42. 8 


63.6 


82.0 


3 


6.4 


39.8 


60.8 


86.7 


1 


6.6 


55.0 


74.0 


96.0 


1918 — Rams . 


5 
3 


8.3 

8.2 


59.9 
56.5 


82. 7 
69.0 


109. 4 

104. 7 


6 
3 


7.1 

5.8 


49.1 
42.5 


77.3 
6S.2 


119.8 
111.7 












Ewes. . 


1 


5.7 


39.6 


61.0 


83.0 


1919— Rams . 


9 


8.0 


54.4 


65.1 


100.2 


5 


7.3 


45.6 


60.6 


97. 8 


4 


6.6 


55. 1 


66.3 


97.0 


Ewes.. 


13 


8.1 


53.2 


66. 5 


91.2 


8 


6.6 


50.7 


64.9 


90.3 


3 


6.7 


53.5 


68. 7 


92.7 


1920— Rams . 


7 


8.4 


60.3 


82.0 


124.5 


14 


7.2 


51.0 


78.9 


117.5 


1 


6.8 


40.0 


67.0 


106.0 


Ewes.. 


17 


8.3 


47.8 


64.5 


98.8 


17 


6.5 


44.8 


64.8 


L02.3 


2 


6.9 


55. 5 


70.0 


92.0 


Average: 
Rams 


23 


8.2 


56.2 


74.4 


109.2 


28 


7.2 


49.0 


74.7 


112.0 


7' 


6.5 


is. 3 


66.8 


96.8 


Ewes 


41 


8.1 


49.2 


65.3 


93.6 


31 


6.5 


45.6 


64. 8 


9S.6 


7 


6.6 


52. 2 


68.7 


91.6 


Average: 
All rams... 


41 


8.4 


59.9 


81.7 


115.3 


53 


7.6 


53. 2 


78.7 


116.3 


13 


7.0 


52. 8 


75.7 


105.9 


All ewes... 


73 


8.4 


53.6 


70.9 


99.8 


60 


6.9 


47.3 


66.7 


102.3 


20 


7.1 


58. 6 


75.9 


104. 7 


All lambs.. 


114 


S.4 


55.9 


74.8 


105.8 


113 


7.2 


50. 2 


72.3 


L09.5 


33 


7.1 


56.9 


75.9 


105.2 



1 Placed in special experiment and weight not comparable. 
SUMMARY. 

1. Feeding at breeding time to increase the number of twins pro- 
duced by ewes is called "flushing." 

2. The percentage of lambs produced by a flock depends upon the 
number of dry ewes and the proportion of ewes producing twins 
and triplets. 

3. The practical advantage of flushing lies in the production of 
twins, which in turn depends upon the number of ova produced by 
the ewe. 

4. Experiments reported herein indicate that ewes getting in lamb 
first produce the largest percentage of twins. 

5. Data from experimental work indicate that ewes should gain 
at least 7 pounds a head during the breeding season to obtain largest 
percentage of twins. 

6. There seems to be a natural tendency toward twin production, 
which varies in different breeds. 

7. It is only in extreme cases that the ram has shown any influence 
on the number of twin lambs produced by the flock. 



14 BULLETIN 996, U. S. DEPARTMENT OF AGRICULTURE. 

8. Records do not indicate that ewes born twins of twin parentage 
are more prolific than single ewes. 

9. There is no material difference in the size of twins and singles 
when fully developed. 

10. Although at market age twin lambs would not weigh so much 
as singles, the difference in weight would be small compared to the 
total weight of the lambs for sale, thus making twins far more profit- 
able. 



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